RAID is mostly used for two things, Redundancy & Speed of Input-Output operations on the data.There are different types of RAID Configurations which can be used on a computer/server.
They Consist of RAID 0, RAID 1, RAID 2, RAID3, RAID 4, RAID 5, RAID 6, RAID 10(1+0) etcRAID 0: RAID 0 is used by a user or a company on its servers when it only needs speed for their I/O operations. It does not provide any Data Security i.e. if one drive fails, all the data is lost. RAID 0 is based on the stripping of data but again has no fault tolerance.RAID 1: RAID 1 is used by users when their DATA Accuracy/Integrity is of highest priority. RAID 1 copies the same data on multiple drives. Even though the reading speed increases as data can be read from any drives, the writing speed remains the same as the lowest writing speed of the drive in the setup/configuration. RAID 1 configurations are also called as Disk Mirroring.
RAID 2: RAID 2 is no longer used. RAID 2 configurations use stripping of Data on many Hard Drives and also use some of them for ECC (Error Checking & Correcting and are called as Parity Drives)
Picture from techtarget
RAID 3: RAID 3 configurations are similar to RAID 2, the difference is that one complete drive out of the Multiple Drives, is Dedicated to Parity Checking/ECC. Data Recovery is possible in this case which is done by calculating the XOR (Exclusive OR) from the rest of the drives. In this config, I/O are all done at the same time.
RAID 4: RAID 4 configurations use large stripes, i.e Data can be read from any single drive. Input-Output overlapping is not possible because all write operations have to update the Parity Disk.
RAID 5: RAID 5 configurations are based on block-level striping with parity. That is, even if one drive fails, the entire array of drives will still function normally. The Performance can take a hit during the REBUILD TIME of the array and can the setup can fail and cause a disk failure.
RAID 6: RAID 6 is almost similar to RAID 5, it includes a second parity scheme that is distributed in the array of drives which rises the cost of this setup/configuration.
RAID 10: RAID 10 is a combination of RAID 1 & RAID 0. There can be two ways, first mirror and then stripe or first stripe and then mirror the data.